(a) Field of the Invention
Broadly speaking, this invention relates to gyroscopically-stabilized, magnetically-slaved heading reference systems. More particularly, in a preferred embodiment, this invention relates to methods and apparatus for calibrating the magnetic sensor used therein.
(b) Discussion of the Prior Art
Most modern military vehicles utilize a heading reference system for navigation and fire control purposes. Typically, such systems are gyroscopically-stabilized and magnetically-slaved, that is they employ a flux valve or magnetic compass. Unfortunately, the magnetic compass in a vehicle is subject to heading errors caused by magnetic deviation. Therefore, the compass must periodically be calibrated so that the known error can be added to or subtracted from the indicated heading to obtain the true magnetic heading.
Existing techniques for calibrating a magnetic compass take several hours and require from 2 to 3 persons. Essentially, they involve swinging the vehicle either manually or electronically, and hence the compass, and comparing the readings obtained against a known standard compass free from deviation error.